Studies on effects of hormones and other activators on adenylate cyclase and NaKMg-ATPase activities in EFA-depleted plasma membranes will continue. It has been reported that insulin activates Mg- stimulated ATPase activity in adipocytes, and NaKMg-ATPase activity in muscle and the epinephrine inhibits liver NaK-ATPase. These are mechanisms by which EFA could affect fatty acid synthesis. Dose response curves to different activators and determination of Km for hormonal activators such as glucagon will be done to learn whether changes in membrane fatty acid composition affect membrane binding of hormones. Phosphatidylserine and phosphatidylinositol are important in glucagon action on liver adenylate cyclase. We have found significant changes in arachidonate levels in these two phospholipids in plasma membranes from EFA-deficient rats. Thus, it will be important to test whether these changes in fatty acid composition affect hormone binding and activation of adenylate cyclase. Further studies on effects of prostaglandins or prostaglandin inhibitors on ion transport oscillations in mitochondria from EFA-deficient rats are planned.